1. Field of the Invention
The present invention includes a display apparatus and a display method and, more particularly, a flat panel display apparatus and a flat panel display method. The invention is also concerned with a display apparatus constructed of a plurality of display devices disposed in the same vertical plane, suitable for a display panel for displaying characters, graphics, patterns, etc. Further, the invention pertains to a display method used in this type of display apparatus.
2. Description of the Related Art
Display apparatuses, such as display panels, can be categorized into large-sized display apparatuses for outdoor use, such as displays for traffic signs, guide signs, public relations, advertisement, time, date, etc., and small and medium-sized display apparatuses, such as monitors for machines used in offices, such as personal computers and word processors, and vehicle-loaded display panels. One type of such a known display apparatus is constructed using electro-optical conversion devices as display devices.
The display apparatuses of this electro-optical conversion type include flat panel display apparatuses and solid-state pixel display apparatuses, such as liquid crystal displays (LCD), plasma display panels (PDP), and electroluminescence displays (ELD). The flat panel display apparatus is constructed of a plurality of very minute display devices disposed in a plane in a two-dimensional matrix form and are operable according to the following dot sequential driving method. Only the very minute display devices located at the activated rows and columns are driven for a short period of time, and such activated rows and columns are sequentially shifted to adjacent display devices, which are then driven for a short period of time. This operation can be continuously repeated to form an image with a minimal number of drivers.
According to this method, the individual display devices are sequentially driven in a time-division manner. Accordingly, one display device forming each pixel is activated only for a short period of time allocated in a time-division manner to perform a display operation by means such as emitting light. Then, after a lapse of a certain period of given time, the light goes off.
FIG. 18 is a block diagram of the above conventional type of flat panel display apparatus. FIG. 19 is a chart illustrating an image signal input into the flat panel display apparatus shown in FIG. 18. An explanation will now be given of the known flat panel display apparatus with reference to FIGS. 18 and 19.
A flat panel display apparatus generally indicated by 51 has a pixel matrix 52, a high-frequency gate driver 53 and a high-frequency signal driver 54, both of which select one of the display devices arranged in rows and columns forming the pixel matrix 52 and excite the selected device, and a controller 55 to supply a display signal to both the drivers 53 and 54.
Input into the controller 55 are an image signal Vd and horizontal/vertical synchronizing signals. The image signal Vd is formed of pixel signals arranged, as illustrated in FIG. 19, in the order of a column, row, and frame in a chronological order. FIG. 19 shows that one frame image is constituted of 14 columns and 16 rows. For example, if a first frame image is represented as shown in FIG. 3, the image signal positioned at the fifth row and fourth column is on, while the adjacent image signal located at the fifth row and fifth column is off. Then, if a second frame image is indicated as illustrated in FIG. 5, the image signal located at the fifth row and fourth column is turned off, while the adjacent image signal at the fifth row and fifth column is turned on.
The image signal Vd, which is modulated by the pixel signals of all the pixels arranged in matrix form, as noted above, has a high frequency ranging from several MHz to several dozens of MHz. Hitherto, images are displayed in such a manner that the high-frequency gate driver 53 and the high-frequency signal driver 54 send output signals to the individual display devices and drive them based on an input high-frequency image signal.
Since the frequency of the image signal rises to as high as several dozens of MHz, the individual display devices are turned on or off in a very short period of time, i.e., the excitation (for example, luminous) period for each display device is extremely short. Accordingly, it is necessary that both the drivers 53 and 54 activate or inactivate a relatively large drive current in a short period of time.
This aspect will be described in greater detail. For example, in a SVGA-specification driver LSI, driving at lower voltages as low as 3.3 V is being promoted due to electromagnetic noise caused by a high-frequency signal input into the driver LSI.
Further, as terminals are mounted on only one side of a panel in response to a higher-definition panel and a narrower-framed module, a driving operation is inevitably performed by using only one side of the panel, thereby increasing the frequency of a signal into the driver LSI. More specifically, although a driving operation is conventionally performed by use of comb-like terminals extended from both upper and lower sides of a panel, all the terminals are now formed only on the upper side of a panel. This makes it possible to reduce the frame area by an amount equal to the lower side of the panel. Because of the construction of a single-sided-driving display apparatus, nearly half of the frame area can be reduced, but on the other hand, the increased frequency band increases the burden on the driver. Additionally, the dot clock speed should be increased in order to achieve high resolution.
The input frequency of a VGA-specification (640 by 480 pixels) single-sided-driving TFT panel having a 26-cm diagonal dimension (10.4 model), which is the mainstream of notebook personal computers, is as high as 25 MHz. Further, the input frequency of a SVGA-specification (800 by 600 pixels) single-sided-driving TFT panel is even as high as 40 MHz, which sharply increases electromagnetic noise. If a XGA-specification (1024 by 768 pixels) single-sided-driving TFT panel is employed, the input frequency even reaches as high as 65 MHz, thereby further increasing electromagnetic noise, causing a serious problem. As a consequence, some measures must be taken in the overall drive circuit of a liquid crystal panel, for example, a smoothly formed input waveform is implemented, to reduce electromagnetic noise.
Another type of conventional display apparatus, which is an electro-mechanical type, has been developed or proposed. As an example of the above type of apparatus, a large-sized display apparatus for outdoor use or a medium-sized display apparatus, such as the one disclosed in Japanese Patent Publication No. 57-31147, is proposed. This display apparatus is constructed, as shown in FIG. 20, in the following manner. A cage-like rotary display unit 151 formed of a synthetic resin material has side faces 152 and 153 opposedly facing each other on which display surfaces of different colors, for example, red and white, are formed. This display unit 151 is rotated by a motor 154 so as to position either of the side faces 151 or 152 on the upper side of FIG. 20 in response to the on or off state of pixels, so that the red or white color can be visually recognized.
Moreover, a small-sized display apparatus, such as the one disclosed in Japanese Patent Publication No. 61-58835, is configured, as shown in FIG. 21, in the following manner. A movable segment 61 provided for part of a rotatable permanent magnet 62 masks a colored display plate 60 in accordance with the rotation of the permanent magnet 62. Accordingly, desired numerical and characters can be displayed by an unmasked portion of the display plate 60. The permanent magnet 62 is rotated by magnetization of an electromagnet 64 achieved by supplying power to a magnetization coil 63.
More specifically, the electromagnet 64 is magnetized by a current pulse flowing in the magnetization coil 63. The electromagnet 64 is magnetized with polarity, i.e., S or N, in the same direction as the current pulse supplied to the magnetization coil 63. Thus, the magnetized electromagnet 64 attracts one end of the permanent magnet 62 with the opposite polarity and repels the other end with the same polarity. The electromagnet 62 is rotated in this manner.
As is clearly seen from the foregoing description, the following image reproducing method is employed in the aforedescribed known electro-optical conversion-type flat panel display apparatuses, such as display apparatuses serving as monitors for machines used in offices, for example, personal computers, word processors, etc. That is, images are expressed by causing pixels on a display to emit light in response to an image signal of several MHz or by covering or uncovering backlight. Accordingly, power consumption required for luminous pixels is increased in response to the increased number of pixels necessitated by a larger screen and higher definition. This hampers the implementation of lower-powered display apparatuses, which are indispensable for portable terminals, such as the personal digital assistance (PDA).
Also, higher-frequency drive signals produce various adverse influences on peripheral circuits, such as occurrence of electromagnetic noise. Further, a wide-band high-frequency driver circuit with high output for switching signals on or off at a high frequency is required, thereby increasing power consumption. This causes increased cost, as well as application restrictions of such a display apparatus for portable terminals. Additionally, inexpensive display devices, such as those with slow response to high speed, may not be readily used in higher-speed display apparatuses.
The electro-mechanical type display apparatus also presents the following problems. Graphics and character patterns are formed in this type of apparatus in the following manner as described above. A rotary display unit has two different-colored display surfaces disposed with respect to a plane including a rotation axis, and the display unit is rotated so that either of the colored display surfaces can be positioned to be recognizable. With this construction, a power supply is unnecessary for such a display apparatus as long as the stable display state is maintained, and thus, power saving can be enhanced in this apparatus as compared with an electro-optical conversion-type display apparatus. Accordingly, this electro-mechanical type display apparatus is suitable for large-sized clocks and for outdoor use, such as in a stadium, for displaying scores and the lapse of time. On the other hand, additional components, such as a rotation mechanism and a motor, are required, resulting in an enlarged apparatus. Additionally, it is difficult to shorten the time required for a rotating operation, thereby decreasing the response speed.
Moreover, the following problem is encountered by a display apparatus developed as a monitor for machines used in offices, such as personal computers and word processors, which is constructed to form images in the following manner. An activated or inactivated pixel signal is supplied to a magnetization coil to magnetize an electromagnet, which further attracts or repels a permanent magnet to rotate it. In response to this rotation, a segment provided for the magnet is moved to cover or uncover a display plate. Additional components, such as a rotation mechanism, are also required for this type of apparatus, thereby increasing the size and cost of the apparatus. In addition to various inconveniences, such as a short lifetime and breakdowns, caused by the rotation mechanism, it is hard to shorten the time required for a rotating operation, thereby decreasing the response speed.